Insulin must be provided to people with Type I and many with Type II diabetes. Traditionally, since it cannot be taken orally, insulin has been injected with a syringe. More recently, use of external infusion pump therapy has been increasing, especially for delivering insulin for diabetics using devices worn on a belt, in a pocket, or the like, with the insulin delivered via a catheter with a percutaneous needle or cannula placed in the subcutaneous tissue. For example, as of 1995, less than 5% of Type I diabetics in the United States were using pump therapy. There are now about 7% of the currently over 900,000 Type I diabetics in the U.S. using insulin pump therapy, and the percentage is now growing at an absolute rate of over 2% each year. Moreover, the number of Type I diabetics is growing at 3% or more per year. In addition, growing numbers of insulin using Type II diabetics are also using external insulin infusion pumps. Physicians have recognized that continuous infusion provides greater control of a diabetic's condition, and are also increasingly prescribing it for patients. In addition, medication pump therapy is becoming more important for the treatment and control of other medical conditions, such as pulmonary hypertension, HIV and cancer. Although offering control pump therapy can suffer from several complications that make use of a pump less desirable for the user.
One drawback is the inability to conceal an external infusion pump and catheter tubing from view. Many users desire to hide the external pump under clothing so as not to seem different from normal people. However, this is inconvenient or impractical, especially for diseases such as diabetes, since a user must have ready access to the external pump for monitoring or administering extra amounts of medication (i.e., boluses during the course of the day). If a user has concealed the external pump, the user must partially undress or carefully maneuver the external pump to a location that permits access to the display and keypad.
A further drawback is the inability to limit the access of the user to certain capabilities. For instance, the user should have access to the keypad so that the user can change the values and parameters of daily pump operation. However, there may be certain parameters that the user should not have access to. This can be especially important, when the pump is being used by children or the elderly. However, if access is very limited, a user may even have to go to the factory and/or to the physician to have the parameters changed.
Another drawback for diabetic pump users, in particular, is the determination of the amount of bolus insulin to be delivered for a meal so as to avoid high blood sugars that would otherwise be caused by the meal. This can be a difficult calculation using formulas and approximations that have several variables that must be measured and calculated. Often, it is easier, but not the best for control, for the user to simply guess what they need rather than to calculate the actual amount of the bolus needed to adequately cover the carbohydrates being consumed. However, in worse case scenarios, guessing can lead to under or overdosing of medication, sometimes with dire consequences.
Another drawback to using an infusion pump, is the step of priming the external infusion pump to remove gas bubbles in the reservoir and/or tubing. The user must first manually shake the reservoir to move any bubbles to the distal end of the reservoir. Then the user must carefully expel the bubbles through the tubing. However, unless all bubbles are moved to the distal end of the reservoir the user will have to expel a larger amount of medication, which can be wasteful, and very costly for special types of medications, such as those used in HIV and cancer treatment. Improved methods of priming the external infusion pump are needed.